In various kinds of control systems a master unit typically controls slave units via a common control bus. Each control unit connected to the bus has a control address (identifier) for identifying the commands addressed to it from among the commands given on the common bus. In a module or circuit card implementing the slave unit, the control address is made by a fixed wiring, or the address can be set, e.g., by switches. Alternatively, every module or card may receive a dedicated control signal from the master unit. A drawback in this known solution is that with otherwise identical cards, it is necessary to know the address set or to be set for each card. The modules and cards used are thus different in respect of production, selling, installation or maintenance, and their installation requires specific settings or tuning.